To get his point across, Bratton even quoted the cautionary lyrics from a hit 1960s Petula Clark song advising against sleeping in the subway.

But critics weren’t interested in how a song from nearly 50 years ago could connect to 2016 subway challenges. Instead, they voiced objections to the idea of having tired subway riders policed right out of their slumber.

For Clark, 83, Bratton summoning up a long-lost hit was a thrill, if not an unexpected one.

NYPD officials Thursday quickly clarified what seemed to be Bratton’s off-the-cuff idea and said 40 winks on a crowded train will still be OK.

“This isn’t something where if you close your eyes on the way to work, in rush hour, you are going to have an officer come and wake you up,” transit police chief Joseph Fox told reporters. “This is a common-sense approach that is an important part of our strategy to combat these crimes.”

Passengers can expect to see more uniformed officers as the NYPD pulls transit cops from desk jobs to patrol in the trains and stations, Fox said. Sleeping will generally be OK, he added.

“If somebody is on a crowded train, they shut their eyes . . . an officer is not going to wake that person,” Fox said.

Fox did say that if a dozing person has a cellphone on his or her lap, cops will wake the individual and say their property is vulnerable to theft. Most of the nudging awake of people on the trains occurs in the overnight hours, something that has been done for years, Fox said.

The crime-fighting program came together fast in response to a recent spate of subway slashings in stations and a spike in crime in the vast train system.

In the view of Patrick Lynch, president of the Patrolman’s Benevolent Association, the plan for a subway wake-up call is nothing more than a distraction by the NYPD to hide the shortage of cops.

“Waking sleeping passengers on a train is an attempt to conceal the fact that we don’t have enough police officers,” said Lynch in a statement. “The NYPD is understaffed and temporarily taking resources from other functions and putting them in the subway is a band aid approach and not a real solution.”